Control-event

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1 Introduction

The control-event package provides the capability to schedule and cancel IO () actions for arbitrary absolute times. Source code is available from hackage[1] and the repository[2].

A shim module that provides identical API as control-timeout (relative expiration times) is available, though it is also much less efficient then either control-timeout or control-event with absolute times.

2 Example Code

Code generally looks like this:

import Control.Monad
import Control.Event
 
main = do
    evtSys <- initEventSystem
    ...
    doStuff action delay race evtSys
 
doStuff action delay race eS = 
    (TOD sec ps) <- getClockTime
    eid <- addEvent eS (TOD (sec + delay) ps) action
    res <- race
    when res (cancelEvent eS eid)
    runUserOperation a

The test code can serve as a decent example as well.

3 Potential Future Changes

• While no work is planned, if someone were looking for a quick project then they could move this package over to the 'time' packages and eliminate the 'old-time' dependency.

4 See Also

• poorly written blog entries [3][4].

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